The present invention relates generally to fluid displacement devices, such as scroll compressors, and more particularly, to an improved scroll type compressor that maintains axial sealing between fixed and orbital scrolls, and maintains perpendicularity of the scrolls to an axis of a shaft driving the compressor.
Scroll type fluid displacement apparatuses, such as scroll compressors, are well known for quietly and efficiently displacing fluid, often from an expanded state to a compressed state, or vice versa. Such devices are increasingly common in systems such as automobile air conditioners.
One such scroll type apparatus is shown in U.S. Pat. No. 3,874,827 to Young, which is incorporated herein by reference. The ""827 patent discloses interfitting spiroidal wraps of two scroll members, which are angularly and radially offset to define one or more moving fluid chambers. By causing one of the scroll members to orbit relative to the other, the apparatus moves the fluid chambers along ribs of the scrolls to change their volume and thus compress or expand the fluid within the chambers.
Until recently, the concept disclosed by Young has not been commercially viable because the machining technology has not been sufficiently sophisticated to produce the curved scroll blades to the required tolerances. If the blades of the moving and fixed scrolls are not machined within required tolerances, fluid leaks and inefficient operation will result.
An axial gap between the scroll members must be sufficiently small (typically less than 0.01 mm) so that an undesirable amount of fluid does not escape. The axial gap between the scroll members is created by, among other things, tolerances in manufacturing of the components of the apparatus. These components must be precisely manufactured and finished to limit such tolerances, which adds to manufacturing costs. However, even small tolerances among various components accumulate to increase the axial gap.
In addition, the scroll members must remain perpendicularly oriented to an axis of a shaft driving orbital movement of the scroll members. Otherwise, axial gaps arise at various contact points between the scroll members, particularly as they move. Also, the scroll members can become misaligned during operation due to manufacturing tolerances, among other reasons. Misalignment of the scroll members also results in accelerated wear of the apparatus components.
The ""827 patent attempts to maintain axial sealing by using a high-pressure fluid porting system with a compliant attachment disk. However, the ""827 patent does not adequately account for manufacturing tolerances within the components of the displacement apparatus, nor does it sufficiently account for maintaining perpendicularity of the scrolls to the axis of the shaft that drives the apparatus.
It is an object of the present invention to provide an improved fluid displacement apparatus, such as an improved scroll compressor, that minimizes an axial gap between first and second scroll members to improve compression efficiency.
It is a further object of the invention to provide an improved fluid displacement apparatus, such as an improved scroll compressor, having an axial gap that can be reduced after assembly of the compressor.
It is a further object of the present invention to provide an improved fluid displacement apparatus, such as an improved scroll compressor, that helps to maintain perpendicularity between the scroll marks and an axis of rotation, to improve compression efficiency and to reduce wear of the compressor.
The present invention overcomes the shortcomings of the prior art by providing an improved scroll type fluid displacement apparatus, particularly a compressor, that maintains axial sealing between fixed and orbital scrolls to increase operation efficiency. The present invention also helps maintain perpendicularity between the scrolls and the shaft axis, increases balance of operation of the apparatus, and reduces operational wear of the apparatus.
In a first embodiment, the improved scroll type fluid displacement apparatus includes: a housing, a first, fixed scroll having a first base and a first rib portion and a second, orbital scroll having a second base and second rib portions, the rib portions of the first scroll and second scroll being radially and phase-shifted relative to one another to contact in a plurality of points to define, with the base of the first and second scrolls, at least one fluid chamber. Also included is an adjustable mechanism for exerting pressure to and between the first and second scrolls to reduce an axial gap between opposing portions of the first scroll and the ribs of the second scroll, to keep the axial gap less than a defined amount for axial sealing of the fluid chamber.
Preferably, the adjustment mechanism includes at least three equidistant adjustment fasteners engaging corresponding bores, which extend axially through the housing. These fasteners can preferably be adjusted after assembly of the apparatus. In a further preferred embodiment, the fasteners are disposed within the apparatus to contact and load bosses contained on a thrust bearing that is included to resist axial thrust between the scrolls.
In another embodiment, the improved scroll type fluid displacement apparatus includes an orbital scroll having at least two portions of significantly different densities. The preferably bimetallic orbital scroll includes a hub or supporting portion surrounding the eccentric bearing having significantly greater density than a connected or integrally formed scroll portion. As a result, the center of mass of the orbital scroll is located at or near the supporting portion. This feature maintains the orbital balance of the second scroll, and thus maintains the perpendicularly of the orbital scroll to the axis of rotation.
In yet another embodiment, the supporting portion of the orbital scroll is manufactured of a material having a lower thermal expansion coefficient than that of the scroll portion. By reducing expansion of the supporting portion surrounding the eccentric bearing, misalignment of the orbital scroll relative to the eccentric bearing is reduced, thus maintaining perpendicularity of the orbital scroll to the axis of rotation and reducing total indicator runout.